Effect of inhomogeneous broadening on threshold current of GaN-based green laser diodes

The inhomogeneous broadening parameter and the internal loss of green LDs are determined by experiments and theoretical fitting. It is found that the inhomogeneous broadening plays an important role on the threshold current density of green LDs. The green LD with large inhomogeneous broadening even cannot lase. Therefore, reducing inhomogeneous broadening is a key issue to improve the performance of green LDs.

Different influences of u-InGaN upper waveguide on the performance of GaN-based blue and green laser diodes

Performances of blue and green laser diodes（LDs） with different u-InGaN upper waveguides（UWGs） are investigated theoretically by using LASTIP. It is found that the slope efficiency（SE） of blue LD decreases due to great optical loss when the indium content of u-InGaN UWG is more than 0.02, although its leakage current decreases obviously. Meanwhile the SE of the green LD increases when the indium content of u-InGaN UWG is varied from 0 to 0.05, which is attributed to the reduction of leakage current and the small increase of optical loss. Therefore, a new blue LD structure with In（0.05） Ga（0.95）N lower waveguide（LWG） is designed to reduce the optical loss, and its slope efficiency is improved significantly.

Room-temperature continuous-wave operation of GaN-based blue-violet laser diodes with a lifetime longer than 1000h

GaN-based continuous-wave operated blue-violet laser diodes(LDs) with long lifetime are demonstrated, which are grown on a c-plane GaN substrate by metal organic chemical vapor deposition with a 10 × 600 μm^2 ridge waveguide structure.The electrical and optical characteristics of a blue-violet LD are investigated under direct-current injection at room temperature(25 °C). The stimulated emission wavelength and peak optical power of the LD are around 413 nm and over 600 mW, respectively.In addition, the threshold current density and voltage are as small as 1.46 kA/cm^2 and 4.1 V, respectively. Moreover, the lifetime is longer than 1000 hours under room-temperature continuous-wave operation.

Performance Improvement of GaN-Based Violet Laser Diodes

The influences of InGaN/GaN multiple quantum wells (MQWs) and AlGaN electron-blocking layers (EBL) on the performance of GaN-based violet laser diodes are investigated. Compared with the InGaN/GaN MQWs grown at two different temperatures, the same-temperature growth of InGaN well and GaN barrier layers has a positive effect on the threshold current and slope efficiency of laser diodes, indicating that the quality of MQWs is improved. In addition, the performance of GaN laser diodes could be further improved by increasing Al content in the AlGaN EBL due to the fact that the electron leakage current could be reduced by properly increasing the barrier height of AlGaN EBL. The violet laser diode with a peak output power of 20 W is obtained.

Effect of Green Quantum Well Number on Properties of Green GaN-Based Light-Emitting Diodes

In GaN-based green light-emitting diodes（LEDs） with different green quantum well numbers grown on Si（111）substrates by metal organic chemical vapor deposition are investigated. It is observed that V-shaped pits appear in the AFM images with the green quantum well number increasing from 5 to 9, and results in larger reverse-bias leakage current. Meanwhile, in the case of the sample with the number from 5 to 7 then to 9, the external quantum efficiency increases firstly, and then decreases. These phenomena may be related to the size of V-shaped pits in the active area and the distribution of electrons and holes in the active area caused by V-shaped pits. The optimal number of green quantum wells is determined to be 7.

Fabrication of room temperature continuous-wave operation GaN-based ultraviolet laser diodes

Two kinds of continuous-wave GaN-based ultraviolet laser diodes（LDs） operated at room temperature and with different emission wavelengths are demonstrated.The LDs epitaxial layers are grown on GaN substrate by metalorganic chemical vapor deposition,with a 10 × 600 μm^2 ridge waveguide structure.The electrical and optical characteristics of the ultraviolet LDs are investigated under direct-current injection at room temperature.The stimulated emission peak wavelength of first LD is 392.9 nm,the threshold current density and voltage is 1.5kA/cm^2 and 5.0 V,respectively.The output light power is 80 mW under the 4.0 kA/cm^2 injection current density.The stimulated emission peak wavelength of second LD is 381.9 nm,the threshold current density the voltage is2.8 kA/cm^2 and 5.5 V,respectively.The output light power is 14 mW under a 4.0 kA/cm^2 injection current density.

GaN基绿光激光二极管发展现状及趋势

由于氮化镓(GaN)基半导体材料在外延生长技术、外延结构设计方面取得了显著的成果,GaN基绿光激光二极管已广泛应用在激光显示、光纤维通讯、生物医疗器件和光数据存储等领域。综述了绿光激光二极管的发展历程及研究现状;重点详述了导致GaN基绿光激光二极管输出功率低、光束质量差及可靠性差等问题的关键因素及解决方法;探讨了绿光波段量子阱的高In组分导致GaN基激光二极管光电性能骤降方面的问题;总结了制备高性能GaN基绿光激光二极管所面临的挑战仍是外延材料质量差、载流子泄漏严重和强极化效应引起的激射效率低等难题。同时,展望了GaN基绿光激光二极管向智能化和模块化方向发展的趋势以及研究重点。

组分阶梯InGaN势垒对绿光激光二极管光电性能的影响

为探究不同铟(In)组分In_(x)Ga_(1-x)N势垒对绿光激光二极管光电性能的影响,本文采用SiLENSe(simulator of light emitters based on nitride semiconductors)仿真软件对一系列具有不同In组分In_(x)Ga_(1-x)N势垒的激光二极管进行研究,结果发现In_(x)Ga_(1-x)N势垒中In组分最佳值为3%,此时结构的斜率效率最高,内部光学损耗最低,光学限制因子最大,性能最优。在具有In_(0.03)Ga_(0.97_N势垒的多量子阱结构基础上,设计了一种组分阶梯(composition step-graded,CSG)InGaN势垒多量子阱结构,提高了激光二极管的斜率效率和电光转换效率,增加了光场限制能力。仿真结果表明,当注入电流为120 mA时,具有CSG InGaN势垒的多量子阱结构,电光转换效率从17.7%提高至19.9%,斜率效率从1.09 mW/mA增加到1.14 mW/mA,光学限制因子从1.58%增加到1.62%。本文的研究为制备高功率GaN基绿光激光二极管提供了理论指导和数据支撑。

20.231 Gbit/s tricolor red/green/blue laser diode based bidirectional signal remodulation visible-light communication system

We propose and experimentally demonstrate a recorded 1-m bidirectional 20.231-Gbit/s tricolor R/G/B laser diode(LD) based visible-light communication(VLC) system supporting signal remodulation. In the signal remodulation system, an LD source is not needed at the client side. The client reuses the downstream signal sent from the central office(CO) and remodulates it to produce the upstream signal. As the LD sources are located at the CO, the laser wavelength and temperature managements at the cost-sensitive client side are not needed.This is the first demonstration, to our knowledge, of a >20 Gbit∕s data rate tricolor R/G/B VLC signal transmission supporting upstream remodulation.

Design of 20 W fiber-coupled green laser diode by Zemax

We represent a design of a 20 W, fiber-coupled diode laser module based on 26 single emitters at 520 nm. The module can produce more than 20 W output power from a standard fiber with core diameter of 400 Hm and numerical aperture （NA） of 0.22. To achieve a 20 W laser beam, the spatial beam combination and polarization beam combination by polarization beam splitter are used to combine output of 26 single emitters into a single beam, and then an aspheric lens is used to couple the combined beam into an optical fiber. The simulation shows that the total coupling efficiency is more than 95%.

Characteristics of InGaN multiple quantum well blue-violet laser diodes

Studies on InGaN multiple quantum well blue-violet laser diodes have been reported. Laser structures with long-period multiple quantum wells were grown by metal-organic chemical vapor deposition. Triple-axis X-ray diffraction (TAXRD) measurements show that the multiple quantum wells were high quality. Ridge waveguide laser diodes were fabricated with cleaved facet mirrors. The laser diodes lase at room temperature under a pulsed current. A threshold current density of 3.3 kA/cm2 and a characteristic temperature T0 of 145 K were observed for the laser diode.

LD泵浦的Nd∶GdVO_4/KTP腔内倍频激光器(英文)

基于对Nd∶GdVO4 晶体热焦距的测量及其 1.0 6 μm激光基本性能 ,用三镜折叠腔研究了半导体激光器 (LD)泵浦的Nd∶GdVO4 /KTP晶体的内腔倍频性质 当用从直径为 2 0 0 μm的单光纤输出的低功率的半导体激光泵浦时 ,绿光的阈值是 2 6mW ,光光转换效率为 17.3% 当用从直径为 1.5 5mm的光纤束输出的高功率的半导体激光泵浦时 ,绿光的阈值是 2 0 0mW ,光光转换效率为 19.35 %

半导体激光端泵腔内倍频Nd:YVO_4/LBO连续波8W绿光激光器(英文)

利用两个半导体激光二极管 ,双端泵浦Nd∶YVO4 晶体 ,LBO采用I类非临界相位匹配、腔内倍频 在 2 8.9W的泵浦功率下 ,获得了 8W连续波 0 .5 32 μm绿光输出 ,其光—光转换效率为 2 7.7%

ZnSe基蓝绿色半导体激光器研究进展

在全彩色显示、高密度激光存储、高速打印、高分辨图像处理和战地生化检测等强力推动下，ZnSe基蓝绿色半导体激光器的研究近年来取得了里程碑式的研究结果．为了明确该领域的研究方向，以便分析在实用化进程中必须解决的主要问题，本文对Znse基蓝绿色半导体激光器及其相关材料的研究进展进行了较全面的评述．作为比较，对GaN基蓝绿色半导体激光器的发展情况和尚待解决的问题也进行了简要评述．

激光二极管泵浦NYAB的绿色激光特性

本文报道了用激光二极管(LD)泵浦自倍频激光晶体 Nd_xY_(1-x)Al_3(BO_3)_4(NYAB)发射0.53μm 绿色激光的实验结果。当用370mW 的泵浦功率激励尺寸为 3mm×3mm×5.7mm 的NYAB 棒时,获得了35mW 的 TEM_(oo)模绿色激光输出。输出波长为0.531μm;总效率为9.5%;斜率效率为24%;光谱线宽为0.11nm;光束腰半径为0.196mm;绿色激光光束偏振度达到98%;光束发散度为1.1mrad。

二极管泵浦高能激光研究进展和展望

高能激光广泛应用于材料加工、科学研究、空间碎片清除、军事应用等领域。二极管泵浦高能激光具有结构紧凑,系统简单、全电驱无限弹仓的特点,近年来,各类二极管泵浦高能激光围绕着同时实现高功率、高效率、高光束质量这一总目标发展迅速。详细综述了国内外高平均功率块状固体激光、高功率可见光波段激光、高峰值功率激光、高功率光纤激光、碱金属蒸气激光等二极管泵浦高能激光的研究进展,并对其发展趋势进行了展望。

半导体激光ICG白蛋白吻合中等动脉实验研究

为取得更好的血管吻合远期通畅率和解决目前激光血管吻合强度不理想的问题，我们应用半导体激光和加靛蓝花青染料（ＩＣＧ）白蛋白，比较三种不同吻合方法：直接吻合法、单纯白蛋白“焊接”吻合法和直接吻合法加焊接吻合法。吻合材料为离体人胸廓内动脉、活体大白鼠腹主动脉及离体猪心脏和胸廓内动脉。结果表明，平均完成一个吻合口的时间为３．１５ｍｉｎ±０．３６ｍｉｎ；使用白蛋白加固或焊接吻合的耐压强度和抗拉强度都显著高于直接吻合法（Ｐ＜０．０５和Ｐ＜０．０１），而且焊接吻合法的热损伤仅限于动脉外膜，深度仅２００μｍ；存活的大白鼠腹主动脉吻合结果满意。激光用于端—侧吻合胸廓内动脉和冠状动脉左前降支，其抗拉强度仍需进一步活体动物实验研究加以改进。

等离子体活性氮源的研制

ZnSe基材料是研制蓝绿色发光器件的首选材料之一。本文报道一种自己研制的、以石英管为主体结构材料的、可适用于ZnSe基材料分子束外延掺杂的简易等离子体活性氛源。该氛源采用射频激励方式激活氮分子。在适当生长条件下，利用装备有该氮源的国产FW－Ⅲ型分子束外延设备，成功地生长出了p型ZnSe优质单晶薄膜。SIMS测量表明，薄膜中氮浓度高达～2．3×1020cm－3；C-V测量表明，净空穴浓度［Na］－［Nd］为～5×1017cm-3，已经达到制备原理性蓝绿色激光二极管的要求（～4．0×1017cm-3）。

Be基蓝绿激光器载流子约束的LCAO理论研究

本征的强离子性，使ZnSe基半导体蓝绿激光器易于形成堆垛层错等退化缺陷，严重地影响了器件的寿命。人们便开始将注意力投向离子性较低的Be基化合物，希望用Be基Ⅱ-Ⅵ族材料取代ZnSe基材料，抑制蓝绿激光器的退化。要研制半导体激光器，电学限制层对发光活性层中载流子的约束能力（即能带的offset值）是最重要的基本参数之一。由于对Be基化合物的了解十分有限，本文从基本的原子参数出发，用原子轨道线性组合（LCAO）理论计算了所有Ⅱ-Ⅵ族化合物价带顶的相对位置，结合带隙的实验值，给出了Ⅱ-Ⅵ族化合物导带底的相对位置。简要分析了二元化合物用于BeTe中载流于约束的可能性。根据虚晶近似，用插值方法计算了与GaAs匹配的Be基四元合金相对与BeTe价带、导带的offset。对各四元合金的特征进行了分析对比，讨论了Be基四元合金用作我流子约束层的可能性。为制作Be基半导体蓝绿激光器提供了能带剪裁的理论依据。

吲哚菁绿染色对980nm半导体激光消融髓核组织效果的影响

目的:观察吲哚菁绿(indocyanine green,ICG)染色对980nm半导体激光消融髓核组织效果的影响。方法:选取新鲜山羊腰椎标本并制成脊柱功能单位(SFU)144个,随机选择24个行预实验,余120个随机分为空白组、蒸馏水组和ICG染色组,每组40个,再根据给予能量不同随机分为5小组。蒸馏水组与ICG染色组分别在髓核内注射100μl蒸馏水或ICG,测定质量后应用980nm半导体激光器分别以总能量70、210、350、490、630J对标本行连续脉冲式激光照射以汽化髓核组织,术后再次测定质量,并计算照射前后标本质量差(髓核消融量)。结果:髓核组织消融量随激光照射能量增大而增多,在70、210、350、490、630J的总能量时空白组的髓核消融量分别为0.0754±0.0046g、0.1170±0.0306g、0.1454±0.0410g、0.1560±0.0058g和0.1742±0.0429g,各能量组间比较P<0.01;蒸馏水组的髓核消融量分别为0.0596±0.0110g、0.0719±0.0228g、0.1246±0.0293g、0.1518±0.0079g和0.2133±0.0513g,各能量组间比较P<0.01;ICG染色组的髓核消融量分别为0.0699±0.0098g、0.1067±0.0154g、0.1978±0.0569g、0.2224±0.0358g和0.2626±0.0241g,各能量组间比较P<0.01。在较低总能量(E<490J)照射下蒸馏水组消融量较其他两组少,而当总能量达630J时,蒸馏水组消融量高于空白组,但仍低于ICG染色组。在相同激光能量照射下,总能量低于350J时,ICG染色组髓核消融量较空白组无明显差别,而当能量高于350J时染色剂组较空白组有显著性差异(P<0.01)。空白组汽化率为0.4mg/J,ICG染色后为0.5mg/J。结论:半导体激光消融髓核组织量随能量增大而增多;ICG可以提高半导体激光的汽化率,在总能量高于350J时ICG染色能够增强980nm半导体激光消融髓核组织的效果。